Copper tubing, plastic pipe and electric conduits are generally cut by a hand saw or by a pipe cutter tool with two guide rollers and a cutting disk that is advanced toward the pipe and the two rollers and is rotated about the axis of the pipe to sever the pipe. Both of these pipe cutting procedures are slow and require substantial physical effort.
The hand saw that is commonly used is a hacksaw. Hacksaws have a thin steel blade held in a frame and subjected to a tension load. These saws are difficult to guide accurately to form a straight cut. Cuts that are perpendicular to a pipe center line are desirable when attaching a pipe to a coupling. If the coupling is threaded, the end of the pipe that is inserted into the coupling must also be threaded. To cut good threads on a pipe, the end of the pipe must be perpendicular to the pipe center line. If the end is not perpendicular the threads may be crooked. A coupling that is connected by solder or adhesives usually includes a flange or stop members that limit penetration of the pipe into the coupling. If the end of the pipe is not perpendicular to the axis of the pipe, the pipe will not seat properly in the coupling.
Hack saw blades have small closely spaced teeth that cut material. These blades remove small particles of material on each cutting stroke and are therefore slow. It can take several minutes to cut one pipe. Even an exceptionally strong person can only cut a limited number of pipes per day due to the force and time required to make each cut.
The pipe cutters that have two rollers and a cutting disk generally work well and require minimal force from the operator. If the axis of the cutting disk is not parallel to the axis of the two rollers, the cutting disk will tend to form a spiral groove and move along the axis of the pipe. A more serious problem that occurs, even when the cutting disk is working properly, is a reduction in the inside diameter of the pipe where the pipe is cut. This reduction in the inside diameter of a cut fluid conveying pipe reduces flow rate and increases the pressure drop along the length of the system when fluid is flowing. The reduced inside diameter in electrical conduit increases the difficulty of pulling wire through the pipe. The ends of the pipe sections with reduced internal diameter have a sharp edge which can damage or even destroy the insulation covering on electrical wiring. The sharp edge can be eliminated with a reamer but the reduced diameter cannot be easily restored to the original diameter. This make it more difficult to pull electrical wires through the pipe and reduces the number or the size of the wires that can be received in the pipe.
Accurate cuts can be made by placing the pipe or rod that is to be cut in a precision machine tool. Due to the size weight and cost of precision machine tools and the time it takes to mount a pipe or rod in the tool and make a cut, it is not feasible to use such machines at a construction site or at a field repair site.
A cut through a tubular member with a hand saw or a powersaw is generally slow at the beginning and at the end. This is due to the large length of the surface in engagement with the saw teeth at the beginning and end of a cut and to the tendency of the saw teeth to fill with material chips and stop cutting.
There is a tendency of some pipes and rods to move in a direction transverse to the direction of the cut, and relative to the saw blade. Such movement results in the cut pipe or rod having an incorrect length. The movement may also result in the cut surface not being in a plane that is perpendicular to the long axis of the pipe or rod. Pipes and rods with outer surfaces that are not cylindrical are even more difficult to cut straight and in the desired location.